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Did anyone make their own riving knife?

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Forum topic by runswithscissors posted 11-08-2014 09:57 PM 3519 views 0 times favorited 49 replies Add to Favorites Watch
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runswithscissors

2183 posts in 1487 days


11-08-2014 09:57 PM

Back in February of 2013 I did a blog about making a riving knife for a Unisaw. Several people said they would like to make their own. I didn’t include any plans, just photos and descriptions of what I did.

My question is whether anyone did follow through and make their own RK. I’d be curious if you came up with any improvements, or ran into any seemingly intractable problems.

I am close to committing to a run of 10 of these, which I will try to sell. So of course I’m also wondering how much of a market there is. At one time, Lee Styron of the Shark Guard system was planning to manufacture them, but then he dropped the idea, without explaining why. I suspect he might have decided the market was too small to justify developing the tooling, etc. to make them. He could be right, in which case I might decide to save myself a few hundred bucks and just continue enjoying my own RK.

So I’d appreciate any feedback. Thanks.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened


49 replies so far

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CudaDude

176 posts in 1770 days


#1 posted 11-08-2014 11:56 PM

Any idea on price? I favorited your blog in hopes of trying to make one someday, but my “want to makes” and “have time to makes” are two totally different things. I would be interested in buying if: It would fit an X5 unisaw and I could afford it.

-- Gary

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AnonymousRequest

861 posts in 1010 days


#2 posted 11-09-2014 12:30 AM

For an older UNI, ‘74? Price?

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runswithscissors

2183 posts in 1487 days


#3 posted 11-09-2014 01:12 AM

A year ago I was thinking $150. But steel prices have gone up, and I haven’t worked out my costs lately. I would have the principal parts cut out via CNC plasma cutter, as I did with a trial run of three or four last year. Some parts I would fabricate myself, and some would be off the shelf, such as the cam clamp for the removable knife. I also would probably supply them with a 14 gauge knife (fits thin kerf perfectly), since a 1/8” blade will work okay with a thinner knife. I could also supply the thicker knife for extra if the customer wanted. But it wouldn’t be hard to make your own.

I haven’t had a look at an X5 saw to see if it would work. The design is configured to bolt to the arbor casting of the original Unis, (‘74, for example) and will be for right tilt saws. I don’t know if Unisaw left tilt saws have a mirror image arbor casting. If so, that wouldn’t be too hard to arrange. But I don’t want to go there yet.

Until I get a close look at a Grizzly 1023, I can’t tell whether it might work on those.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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Handtooler

1373 posts in 1594 days


#4 posted 11-09-2014 01:24 AM

I have the Grizzly G0691 and its riving knife is at least 0.002 in too thick for my Freud Premier thin kerf blade, but really works great for standard kerf blades. So you might well consider the thickness of the stock to improve your market?

-- Russell Pitner Hixson, TN 37343 bassboy40@outlook.com

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Grandpa

3256 posts in 2137 days


#5 posted 11-09-2014 02:52 AM

I have a right tilt Unisaw and I believe it was built around 2003. I couldn’t unearth my information in my desk tonight so I am not certain. I would be interested in talking to you about a RK or detailed plans.

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runswithscissors

2183 posts in 1487 days


#6 posted 11-09-2014 03:56 AM

I use a Freud think kerf (not sure whether it’s a Premier), and the 14 gauge knife is a perfect fit—no slop, no drag.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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runswithscissors

2183 posts in 1487 days


#7 posted 11-25-2014 01:35 AM

Handtooler: you could make your own knife, using the original as a pattern, out of 14 gauge plate steel. Not hard to do.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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Leeway

28 posts in 1938 days


#8 posted 02-02-2015 12:30 AM

I had a few issues when we were working together on this. They were mostly my issues though and I have since solved some of them. I have better cnc equipment and work holding as well as tooling now. In 2013 I had just got my new cnc mill and had just finished up my plasma cutter. That mill burned up last year. The entire control cabinet. I replaced it with a better one.
My mock up Unisaw is still sitting right beside the door with all the parts of your prototype and some of the ones I did manage to work on. I have better CAD and CAM software now as well that will help with clearance issues we were having. It can show conflicts or interference better than what I was using. One stopping point that was in the design was the actual attachment to the trunnion. I think I had that worked out with a threaded aluminum block.
The next was there is a little side to side play at the knife. A throat plate will take care of that if there is no guard on it. With a guard it needs something more.

The two original splitter mounting bracket holes in the back trunnion could be used to mount a track that the knife would slide in. That was where I ran into time constraints with guard production. I might be able to pick it back up in a couple months. If you just need me to plasma cut some parts for your run, I could do that.
Shoot me an email if so.
You did put a lot of work into the design. I think others can certainly benefit from the added safety.

-- Lee

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Redoak49

1944 posts in 1450 days


#9 posted 02-02-2015 02:22 PM

I hope you guys can sell retro fit riving knives. My one objection to old iron is the lack a riving knife and the danger of a kick back. I am glad to see someone working on this.

View Kelly's profile

Kelly

1113 posts in 2406 days


#10 posted 05-03-2016 10:10 PM

Riving knives are no more protection against kickback than are splitters. They are the same thing, except one raises and lowers with the blade, making them more convenient and, in a few situations, usable where the fixed ones aren’t.

Since adding the Merlin Splitter to my cabinet saw, several years back, I haven’t had a kickback. I have had pieces of wood close so hard on the splitter I had to stop.


I hope you guys can sell retro fit riving knives. My one objection to old iron is the lack a riving knife and the danger of a kick back. I am glad to see someone working on this.

- Redoak49


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runswithscissors

2183 posts in 1487 days


#11 posted 05-04-2016 03:35 AM

Wow, an old thread got revived. Kelly, you are right, up to a point. A riving knife is just a high-falutin” splitter. But it does have the advantage of always hugging the blade closely, and not requiring removal for non-through cuts.

I have been continuing with R & D in a desultory sort of way, and now have a design for the base plate (the only function of which is to have something for the articulating arm to rotate on) that only needs to be bolted in place, with no subsequent fooling around with spacing adjustments. Not that the adjustments were so difficult, but it seems better if you don’t have to do that at all.

Lee is right, that there is some flex in the knife, though the ZCI compensates for that quite well. I suspect that all riving knives, due to their nature, will have some flex. Certainly the BORK must, though I haven’t personally met one in the flesh (so to speak).

One question I have been mulling is whether the riving knife is necessary when doing 45 deg. bevel cuts. Obviously it requires a special ZCI for that, and as many ZCIs as the number of different bevel angles you might want to cut. You can’t use the riving knife with the original throat plate, and might be as well off just removing the RK altogether. This is just a matter of a few seconds to do, and then to pop it back in when you are done. I have made myself a ZCI for beveling, but it is a PITA to make, with a lot of smoke and bad language. I would be curious what others think about this. How do the saws with built in RKs do this? Or do they just dispense with the ZCI?

I have also done some work on the knife holder, and have a much improved version. This still requires initial fiddly adjustments at the outset (to align it with the blade), but alternatives I’ve tried introduce their own problems.

Lee (if you are still following this): I never meant to ignore your last post, I just didn’t have a ready response. It’s interesting to me that the initial idea only took about 3 weeks to bring to the prototype stage, but fine tuning it is taking a couple of years or so. I am now on the verge of producing 15 of these, but would prefer not to get into manufacturing. Basic laziness, I guess.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View bbc557ci's profile

bbc557ci

589 posts in 1536 days


#12 posted 05-04-2016 09:44 PM

I thought a splitter was just that, a splitter to prevent binding at the back side of the blade. And thought a riving knife had pawls to prevent a kick back.

Someone please straighten me out on this!!

Thanks -

-- Bill, central NY...no where near the "big apple"

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MrUnix

4211 posts in 1660 days


#13 posted 05-04-2016 09:57 PM

A riving knife is a splitter. A splitter is a splitter. Both do the same. What you are thinking about are anti-kickback pawls, which are typically found on splitters, not riving knives. Here is an example:

(the above is a Delta disappearing splitter for the Unisaw)

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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runswithscissors

2183 posts in 1487 days


#14 posted 05-04-2016 10:24 PM

To distinguish a RK from an ordinary splitter: the RK goes up and down with the blade, and it hugs the back of the blade quite closely (1/8” to 1/4”) during the whole range of motion. Typically, the top of the RK is just a bit lower than the top of the blade. This allows it to be used for non-through, or blind, cuts.The advantage of that is that you seldom have to remove it, as it normally isn’t in the way. Since the traditional splitter/blade guard combo is often in the way, many people remove them permanently to avoid the hassle. I did that myself with my first Rockwell contractor’s saw.

A splitter or RK prevents kickback by preventing the material from contacting the back of the blade, either by pivoting into it accidentally, or by the kerf pinching shut due to release of stresses in the wood structure. In one of my first tests of the RK, I had a piece of rough cut oak pinch shut onto the RK, so I had to stop the cut. It was satisfying to see that thing work as it was supposed to.

I have never been impressed by kickback pawls. Others have expressed concerns about their effectiveness.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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bbc557ci

589 posts in 1536 days


#15 posted 05-05-2016 05:58 AM

Thanks gents for the insight on the splitter vs riving knife. Some time ago I made my own splitter for my Uni and it works perfectly. Splitter, as in doesn’t move up/down with the blade LOL

-- Bill, central NY...no where near the "big apple"

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